Mixing device



H. D- SCHRIER MIXING DEVICE 5 Sheets-Sheet 1 IN VEN TOR. HA A 01 D D.5677 9/67? Jan. 25, 1966 Filed April 17, 1962 Jan. 25, 1966 H. D.SCHRIER 3,

MIXING DEVICE Filed April 17, 1962 3 Sheets-Sheet 2 Elll INVENTOR.

" HAROLD 0 SCHR/ER ZZMMM/WM 4 TTUP/VEYS Jan. 25, 1966 H. D. SCHRIER3,231,242

MIXING DEVICE Filed April 17, 1962 5 Sheets-Sheet 5 II nnl INVENTOR.

. 6 HAROZD 0. SCHR/ER ATTORNEYS United States Patent 3,231,242 MIXINGDEVICE Harold D. Schrier, 3405 Winchell Ave., Kalamazoo, Mich. FiledApr. 17, 1962, Ser. No. 188,203 Claims. (Cl. 259-7) This inventionrelates to improvements in apparatus for mixing materials and, moreparticularly, relates to an apparatus for mixing together a plurality ofsubstances, such as two immiscible liquids, a gas and a liquid, or afluid and a pulverized solid.

The treatment of a plurality of substances to effect a uniform mixingthereof is widely carried out in industry. Such treatments include themixing of a gas and a liquid to form a cellular product, such as a foam,the mixing of two immiscible liquids to form an emulsion and the mixingof fluids with a pulverized solid to form a suspension. Other usesinclude the contacting of two sub stances, for example, to effect achemical reaction therebetween.

The apparatus of the invention was devised particularly to improveprocedures for generating a foam for use with gypsum to form alightweight, foamed, gypsum product which can be used, for example, tomake a door core, wall board or similar known products. Accordingly, thefollowing description will refer specifically thereto. It will beunderstood, however, that such specific description is for illustrativepurposes only and that the invention is useful for a wide variety ofmixing operations.

The formation of a foam intended for use in a gypsum slurry involves themixing of a gas, commonly air, with water containing a foaming agent,such as a foaming agent of the class described in my co-pendingapplication Serial No. 91,587, filed February 27, 1961, now abandoned.Such a foam should be stable, fine-celled and of uniform density. Inorder to produce such foams with the prior art mixing apparatus andmethods, it has been necessary to use a considerably greater amount offoaming agent than theoretically is required to form an acceptable'foam.Thishas been done in order to insure that each part of the foam has atleast the minimum amount of foaming agent therein necessary to providean acceptable foam even though there may be an excess of foaming agentin other parts of the foam.

Further, it is desired to produce a foam having a small average poresize while at the same time providing a high foam production rate for afoaming unit of any given size. This involves a substantial problembecause the formation of a foam involves subdividing relatively largebubbles of gas, such as air, to form smaller bubbles or pores. In orderto reduce the size of the bubbles, it is necessary either to use largermachines so that a greater amount of subdivision can take place or toreduce the clearances between the mixing elements and also to reduce thequantity of the material fed through the machine. This either increasesthe equipment costs or decreases the foam generating capacity of theequipment. Moreover, even these procedures may not have the desiredeffect.

Accordingly, it is an object of this invention to provide a mixingapparatus which is capable of mixing many different types of materialsin an improved manner.

Further, it is an object of this invention to provide a mixingapparatus, as aforesaid, which is capable of effecting a lr'ghlysatisfactory mixing of the materials fed therethrough to thereby producea uniform product.

It is a further object of this invention to provide an apparatus, asaforesaid, which is capable of forming a stable, fine-celled foam ofuniform density, using a minimum amount of foaming agent.

Other objects and advantages of the invention will become apparent topersons acquainted with processes and apparatus of this type uponreading the following description and inspecting the accompanyingdrawings.

In the drawings:

FIGURE 1 is a side elevational view of the apparatus of the inventionand schematically illustrates the means for supplying the material to bemixed thereto.

FIGURE 2 is a simplified, partially broken away, front elevational viewof the apparatus shown in FIGURE 1.

FIGURE 3 is a sectional view taken along the line III-III of FIGURE 2.

FIGURE 4 is a plan view of a fragment of the rotor.

FIGURES 5, 5a and 5b are sectional views taken along the line V-V ofFIGURE 3 and illustrating three difierent positions of one of the mixingelements on the rotor with respect to a stationary mixing element on thecasing.

FIGURE 6 is a sectional View taken along the line VIVI of FIGURE 3.

FIGURE 7 is a sectional view taken along the line VII-VII of FIGURE 5.

General description In general, the invention provides a mixingapparatus in which a stream of the materials to be mixed is continuouslyfed into a casing having a rotor rotatably mounted therein. The rotorhas a pair of axial end faces opposed to the interior surfaces of theend. walls of the casing. Mixing elements are mounted upon both endfaces of the rotor and these mixing elements interfit with correspondingmixing elements on said interior surfaces. The stream of material is fedthrough one of the end walls of the casing and flows radially outwardlybetween one axial end face of the rotor and the end wall of the casingopposed thereto. The stream then passes around the periphery of therotor and flows radially inwardly between the other axial end face ofthe rot-or and the end wall opposed thereto. As the rotor is rotatedwithin the casing, the mixing elements elfect a shearing and agitationof the material passing through the casing. Thus, the materialscomprising the stream are efiectively mixed so that the product exitingfrom the casing consists of a uniform mixture of the materials.

As applied specifically to generation of a foam, a gas, such as air, isinjected into a stream of liquid which contains a foaming agent outsideof the casing and this stream is then fed into the casing where the gasbubbles are subdivided to forma stable, fine-celled foam. Under certaincircumstances, it is acceptable to feed the liquid and the gasseparately into the casing but this is less satisfactory.

The mixing elements are arranged in concentric circular rows on the endfaces of the rotor and on the interior surfaces of the end walls of thecasing. Each mixing element is comprised of a pair of radially spaced,axially projecting legs. The mixing elements within a given row arespaced circumferentially from each other to provide gaps therebetweenand the clearances between the legs of the mixing elements which areassociated with each other are closely controlled so that an effectiveshearing and mixing action takes place.

Detailed description Referring to the drawings, the mixing device 10 iscomprised of a rotor 11 mounted on a shaft 12, which shaft may berotated by any suitable mechanism, such as an electric motor (notshown). The rotor 11 is rotatably supported within a casing 13. Thecasing is comprised of an end plate 14 and a substantially cup-shapedmember 16, said end plate and said cup-shaped member being rigidlyaffixed to each other. The member 16 has an end wall 17 and has acylindrical sidewall 18. The end plate 14 and the end Wall 17 areopposed to and are spaced from each other and the rotor 11 is disposedtherebetween and is encircled by the sidewall 18.

The shaft 12 extends through a central opening 19 in the end wall 17,thence through a central opening 21 in a fitting 22 into and through afurther opening 23 in a housing 24. A recess 26 is provided forreceiving a suitable mechanical seal 27 and a bearing 28. The sealprevents flow of the material being mixed along the shaft 12 in arightward direction as appearing in FIG- URE 3.

The fitting 22 has a substantially radially extending opening 31 towhich a conduit 32 is connected whereby the materials to be mixed can befed into the mixing device 10. The opening 31 comunicates with anannular manifold 33 surrounding the shaft 12. The manifold 33communicates through an annular opening 34 with the central opening 1?in the end wall 17 and thereby with the interior of the casing 13.

The materials to be mixed, which are assumed for the purposes of thepresent disclosure to be a liquid containing a foaming'agcnt, and a gas,are supplied from the sources 36 and 37, respectively. Pressure will beexerted upon both materials, such as by utilizing a pump for pumping theliquid and a compressor for pressurizing the gas, so that both materialsare fed under pressure. The two materials are .fed continuously into amixing valve 38 which may be of any suitable, conventional construction.The two materials are mixed thereby in a preliminary fashion so thatroughly equal amounts of the gas are contained in given amounts of theliquid. The stream exiting from the mixing valve is then fed through theconduit 32 into the interior of the casing 13 where it is mixed as isdescribed in greater detail hereinbelow. If desired or necessary, a pumpmay be provided between the mixing valve 38 and the casing 13 to augmentthe feeding pressure on the stream of material entering the casing. Inany event, sufiicient pressure is exerted on the stream to move samethrough the casing 13.

The rotor 11 is a substantially flat disc and has a series of radiallyspaced, annular, concentric grooves 41 (FIG- URE 4) on both axial facesthereof. The interior faces of the end plate 14 and end wall 17 have asimilar series of radially spaced, annular, concentric grooves 42 and43, respectively, therein. Each of the grooves 42 and 43 is associatedwith but is offset radially, here radially inwardly, from one of thegrooves 41 on the rotor 11.

A plurality of U-shaped mixing elements 46 are disposed in each of thegrooves 41 and similar U-shaped mixing elements 47 and 48 are disposedin each of the grooves 42 and 43, respectively. The mixing elements 46on the rotor 11 interfit with the mixing elements 47 and 48 on the endplate 14 and end wall 17, as described in greater detail hereinbelow, toeffect a thorough mixing of the fluid stream which is fed through thecasing 13.

As best illustrated in FIGURE 4 wherein one axial face of the rotor 11is shown, the number of mixing elements 46 in the grooves 41 increasestoward the periphery of the rotor. Further, the arcuate distance betweenany two adjacent mixing elements in any given groove 41 is differentfrom the corresponding spacing of the mixing elements in the adjacentgrooves. While the number of mixing elements in any two adjacent groovesmay be the same, the radially outermost grooves have a substantiallygreater number of mixing elements than do the radially innermostgrooves. Moreover, the mixing elements 46 in any given groove 41 areoffset circumferentially from the mixing elements in the grooves 41adjacent thereto. This arrangement of the mixing elements 46 insuresthat no channeling or uncontrolled motion of the stream being mixed willoccur and, thereby, different parts of the fluid stream will all besubjected to substantially the same type and amount of mixing action.

For convenience in manufacture, each of the mixing elements 46 on one ofthe axial faces of the rotor 11 is arranged in back-to-back relationshipwith a mixing ele- 4 ment on the other face so that they may be securedto the rotor by a common rivet, as described hereinbelow. However, thissingle rivet feature is not essential for the purposes of the invention.

The mixing elements 47 and 48 on end plate 14 and end wall 17 arearranged in the grooves 42 and 43, respectively, in the same fashion asare the mixing elements 46 in the grooves 41. The number of mixingelements 47 and 48 in any of the grooves 42 and 43 may be equal to ordiiferent from the number of mixing elements 46 in the grooves 41associated therewith. However, the number of the mixing elements in thegrooves 42 and 43 also increases toward the periphery of the end plate14 and end wall 17, respectively. Further, the mixing elements inadjacent grooves'42 or 43 are offset circumferentially from each otherfor the reasons previously discussed. As shown in FIGURE 3, each of themixing elements 47 is axially aligned with a mixing element 48 but thisarrangement is not essential.

The mixing elements 46 are identical. They are substantially U-shapedand each has a long leg 51, a short leg 52 and a connecting web 53. Themixing elements '47 and 48 are substantially identical to the mixingelements 46 and corresponding parts thereof are identified by the samereference numerals with a sufiix a and b applied thereto, respectively.The mixing elements 46 are arranged with their webs 53 disposed in anappropriate one of the grooves 41 with the legs 51 and 52 thereofprojecting axially. The short legs 52 are in this embodiment arranged onthe radially inner side of the groove 41 and the long legs 51 are on theradially outer side of the groove, although this arrangement may bereversed if desired. The mixing elements 47 and 48 are similarlyarranged except that the long legs 51a and 51b are on the radially innerside of the grooves 42 and 43 and the short legs 52a and 52b are on theradially outer side of said grooves. Thus, the short legs 52 of themixing elements 46 are adapted to travel between the legs of the mixingelements 47 or 48 associated therewith. Similarly, the short legs of themixing elements 46 and 47 are adapted to extend between the legs of themixing elements 46 which are associated therewith. Further details ofthe shape and orientation of the legs will be pointed out hereinafter.

The mixing elements 46, 47 and 48 are fixedly secured to the rotor 11,end plate 14 and end Wall 17, respectively, in a carefully controlledmanner to insure proper spacing therebetween. As best shown in FIGURE 6,two axially aligned mixing elements 46 on opposite axial faces of therotor 11 are secured to said rotor by a rivet 56 which passes throughsaid rotor. The rivet 56 has a pair of enlarged heads 57 and 58 whichoverlie the webs 53 of the two mixing elements 46 and thereby fixedlyhold said mixing elements in the grooves 41. Similarly, rivets 59 and 61fixedly secure the mixing elements 47 and 48 in the grooves 42 and 43.The enlarged heads 62 and 63 on rivets 59 and 61 overlie the webs 53aand 53b and the enlarged heads 64 and 66 overlie the axially-remotesurfaces of the end plate 14 and end wall 17.

After the initial riveting operation during which at least one of theenlarged heads above referred to is formed on each rivet, the heads 57,58, 62 and 63 are cold-formed so as to have aprecise shape,particularly, a precise axial depth. Such cold forming can be carriedout by a coining or similar die-shaping operation. Thus, the spacingbetween the free ends of the short legs 52, 52a and 52b and the opposingsurface of rivet heads 57, 58, 62 and 63 is precisely controlled. Wherea fine-celled foam is to be generated, the spacing between the ends ofthe short legs and the rivet heads is made as small as possibleconsistent with providing a running clearance therebetween. If acoarser-celled foam is to be generated, this spacing could be larger.

As shown in FIGURES 5, 5a and 5b, the surfaces 71, 72, 73 and 74 withthe legs 51a and 52a of mixing element 47 are planar and parallel witheach other. Similarly, the surfaces 76, 77, 78 and 79 of the legs 51 and52 of mixing element 46 are planar and parallel with each other. Theradially innermost legs 52 and 51a are tangent to the circular inneredge of the grooves 41 and 42 in which they are mounted while theradially outermost legs 51 and 52a extend chordally with respect to thecircular outer edge of the groove within which they are mounted. Sincethe grooves are concentric, the legs 51, 52, 51a and 52a will beparallel when they are radially aligned with each other. The legs 51band 52b of mixing elements 48 are arranged in the same fashion as legs51a and 52a.

Still referring to FIGURE 5, 5a and 5b, during rotation of the rotor 11,the short leg 52 of the mixing element 46 will pass between the legs 51aand 52a of the stationary mixing element 47. Because of the planarconfiguration of the legs, and the positioning thereof as describedabove, When the leg 52 is about to enter between the legs 51a and 52a,or is leaving same, the surface 78 thereof is spaced from the opposingsurface 73 of leg 52a a distance a (FIGURES 5 and 5b) and the surface 79is spaced from the opposing surface 72 of the leg 51a a distance c. thelegs 51a and 52a and is parallel therewith, as shown in FIGURE So, it isspaced from both such legs a distance b. Distance a is less thandistance b and distance b in turn is less than distance c. Accord- Whenthe leg 52 is fully received between ingly, as the short leg 52 passesbetween the legs 51a and 52a, different clearances will exist betweensuch legs at various times and, thus, the shearing effect caused bymovement of said leg 52 will vary in intensity. This has been found toimprove the mixing operation and also provides a smaller and moreuniform size when a foam is being generated.

The end plate 14 has a central outlet opening 81 to which is connected adischarge conduit 82. The discharge conduit 82 has a constriction ofsubstantially uniform cross-sectional area therein for the purpose ofretarding flow of material from the casing 13. This insures that thefeeding pressure will remain effective on the materials within thecasing so that the mixing of said materials will be performed underpressure. Here, the constriction is provided by a portion 84 of reducedinternal diameter in the discharge conduit 82. While the particularmanner of providing the constriction may be varied, it has been foundthat the constriction should be of substantially uniform cross-sectionalarea, particularly where a foam is being generated, in order not todetrimentally effect the uniformity of the stream of material exitingfrom the casing.

Operation While the operation of the machine has been indicated before,the same will now be summarized to insure a complete understanding ofthe invention.

The stream of materials to be mixed is continuously fed under pressureand passes through the conduit 32 into the manifold 33, thence into thecasing 13 in the form of an annular stream. The stream flows radiallyoutwardly between the rotor 11 and the end wall 17, thence around theperiphery of the rotor 11 and then radially inwardly between the rotorand the end wall 14 from whence it passes outwardly through the conduit82. In moving through the casing 13 as above described, the entirestream does not necessarily move only radially through a completelytortuous path around the free ends of the legs of all of the mixingelements 46, 47 and 48 because of the gaps between the mixing elements.However, a substantial and controlling amount of movement of the streamdoes involve such a tortuous movement. During such tortuous movement,the stream in passing between the adjacent legs of two mixing elementsand then around the free ends of the legs is subjected to an intenseshearing action. This shearing action is particu- 6 larly intense wherethe stream passes between the free end of the short legs 52, 52a and 52band the rivet heads opposed thereto. The clearance between the shortlegs and the rivet heads is carefully determined in order to provide thedesired shearing action.

While the basic movement of the material is in a radial direction withrespect to the rotor 11, the material also will be movedcircumferentially to some extent by the mixing elements as the rotor 11rotates within the casing and this further increases the elfectivenessof the mixing operation. The extent to which various portions of thestream are mixed with each other also is enhanced by the gaps betweenthe mixing elements which permit a limited amount of freecircumferential and radial movement of portions of the stream. However,since these gaps are small and are staggered, only a small amount of thematerial can move therethrough and any material which does move througha gap will be picked up and acted on by the adjacent radially outerteeth. Hence all portions of the stream will be mixed to a substantiallyuniform extent.

When the stream of materials is moved circumferentially within thecasing, it is driven against the end surfaces of the mixing elements andpasses around the sharp corners thereof. This improves the subidivisionof the stream. For example, referring to FIGURE 5, the stream ofmaterials contacts and is broken up as it passes around the sharpcorners 86, 87, 88 and 89 of the legs 51 and 52 and the sharp corners91, 92, 93 and 94 of the legs 51a and 52a. Further, referring to FIGURE7, some of the material travels circumferentially within the groove 42and this is driven against the end surface of the web 53a and thenpasses around the sharp corner 96 thence around the corner 97 of therivet as indicated by the arrow A. Thus, a portion of the stream passingbetween the legs of any mixing element is contacted by six sharp edges,for example, the edges 92, 93, 88, 89, 96 and 97.

It is to be noted that the pressure on any given portion of the materialvaries somewhat from time to time because of the gaps between the mixingelements and because of the way the legs of the mixing elements areshaped and disposed. Thus, as shown in FIGURES 5, 5a and 5b, because ofthe different clearances which exist at different times between the legsof a given pair of mixing elements as they move relatively to eachother, different pressures will be exerted on the material therebetweenand the intensity of the shearing effect also will vary.

Thus, as the stream flows radially with respect to the rotor 11 it issubjected to an intense shearing by the relative movement between themixing elements. At the same time, because of the gaps between the legs,there is some freedom of movement so that different parts of thematerial can be mixed effectively with each other. Further, variableshearing forces and pressures are exerted upon the material as it flowstherethrough.

Considering an operation in which a foam is generated, the liquidcontaining the foaming agent and the gas, which have been previouslymixed together at least in a rough fashion, are continuously fed as astream through the casing 13. As this stream passes through the casing,the gas bubbles are continuously subdivided by the shearing action abovedescribed and the materials are mixed in an eifective manner whereby thefoam product has small gas bubbles uniformly distributed therethrough.It has been found that by the use of the present invention, the amountof foaming agent which is required to produce a stable, uniform foam issubstantially less than where other types of foam generating apparatusare used, other conditions remaining the same.

While a particular preferred embodiment of the invention has beendescribed, the invention contemplates such changes or modificationstherein as lie within the scope of the appended claims.

What is claimed is:

1. A mixing apparatus comprising:

a hollow casing having a pair of axially spaced end walls and aperipheral Wall extending therebetween;

a rotor rotatably mounted within said casing, said rotor having a pairof axial end faces disposed in face-to-face, spaced-apart relation withrespect to the interior surfaces of said end walls;

means for admitting a stream of material to be mixed through one of saidend walls into the interior of said casing; means permittng removal ofthe stream of material through the other end wall of said casing;

substantially U-shaped mixing elements mounted on the end faces of saidrotor and on the interior surfaces of said end walls, said mixingelements being arranged in concentric rows with the mixing elements inany given row being circumferentially spaced from each other, each ofsaid mixing elements comprising a pair of radially aligned and radiallyspaced legs connected by a web, the Webs of said mixing elements beingmounted on said end faces and said interior surfaces, respectively, andprojecting thereabove, the radial spacing between the legs of eachmixing element being substantially greater than the radial thickness ofthe legs whereby when the legs of any one mixing element are interfittedwith the legs of another mixing element spaces of substantial width areformed between adjacent legs;

fasteningmeans securing the web of each of said mixing elements to itsassociated end face or interior surface, said fastening means having anenlarged head overlying and projecting away from the web of itsassociated mixing element, said head having a diameter substantiallylarger than the radial width of the legs, said head being spaced apredetermined axial distance from the free ends of the legs of themixing elements opposed thereto;

the rows of mixing elements on said rotor being offset radially from therows of mixing elements on said internal surfaces so that the legs ofthe mixing elements in any given row are interfitted with and overlapthe legs on the mixing elements opposed thereto, whereby, when saidrotor is rotated, each time a leg of one mixing element moves betweenthe legs of the mixing element opposed thereto the material beingforwarded through the casing will be moved into the spaces between thelegs and against an edge of the web and thence between the head and thefree end of the mixing element leg so that the material will besubjected to an intensive shearing and a variable compression in orderto effect a uniform mixing thereof.

2. A mixing apparatus according to claim 1, in which the fastening meansis a rivet and the mixing elements each have a long leg and a short leg,the short leg of any given mixing element being receivable between thelegs of the mixing element opposed thereto and extending close to therivet head thereon.

3. A mixing apparatus, comprising:

a hollow casing having a pair of axially spaced end walls and aperipheral wall extending therebetween;

a rotor rotatably mounted within said casing, said rotor having a pairof axial end faces disposed in face-toface, spaced-apart relation withrespect to the interior surfaces of said end walls;

means for admitting a stream of material to be mixed through one of saidend walls into the interior of said casing;

means permitting removal of the stream of material through the other endwall of said casing;

mixing elements mounted on the end faces of said rotor and on theinterior surfaces of said end walls, said mixing elements being arrangedin concentric rows with the mixing elements in any given row beingcircumferentially spaced from each other, each of said mixing elementscomprising a pair of radially aligned and radially spaced legs, the rowsof mixing elements on said rotor being offset radially from the rows ofmixing elements on said internal surfaces so that the legs on the mixingelements in any given row are interfitted with and overlap the legs onthe mixing elements opposed thereto;

the legs of said mixing elements having planar, parallel,

radially inner and outer surfaces which extend in a chordal directionwith respect to the rotor; whereby, when the rotor is rotated, each timeone leg of one mixing element moves between the legs of a mixing elementopposed thereto there will be a changing clearance between the legs sothat the material will be subjected to a variable compression.

4. A mixing apparatus according to claim 3, in which the mixing elementsare substantially U-shaped and have webs mounted on said end faces andsaid interior surfaces, respectively, and projecting therebeyond;

a rivet securing the web of each of said mixing ele- 5 ments to itsassociated end face or interior surface, said rivet having an enlarged,cold-formed head overlying and projecting away from the web of itsassociated mixing element, the rivet heads being spaced a predeterminedaxial distance from the free ends of the legs opposed thereto, the websbeing spaced a greater distance than said heads from said free ends andthe rotor face and said interior surfaces are spaced an even greaterdistance from said free ends;

whereby, when the rotor is rotated, each time one leg of one mixingelement moves between the legs of a mixing element opposed thereto thematerial will be moved against an edge of the web of said latter mixingelement and thence between the rivet head and the free end of said oneleg so that the material will be subjected to an intensive shearing andvariable compression in order to effect a uniform mixing thereof.

5. A mixing apparatus according to claim 3, in which said end faces andsaid interior surfaces each having a pluralityof radially spaced,concentric, annular grooves therein and said mixing elements are mountedat circumferentially spaced points in said grooves, said surfaces ofsaid legs extending in a chordal direction in said grooves.

WALTER A. SCHEEL, Primary Examiner.

IRVING BUNEVICH, CHARLES A. WILLMUTH,

Examiners.

1. A MIXING APPARATUS COMPRISING: A HOLLOW CASING HAVING A PAIR OFAXIALLY SPACED END WALLS AND A PERIPHERAL WALL EXTENDING THEREBETWEEN; AROTOR ROTATABLY MOUNTED WITHIN SAID CASING, SAID ROTOR HAVING A PAIR OFAXIAL END FACES DISPOSED IN FACE-TO-FACE, SPACED-APART RELATION WITHRESPECT TO THE INTERIOR SURFACES OF SAID END WALLS; MEANS FOR ADMITTINGA STREAM OF MATERIAL TO BE MIXED THROUGH ONE OF SAID END WALLS INTO THEINTERIOR OF SAID CASING, MEANS PERMITTING REMOVAL OF THE STREAM OFMATERIAL THROUGH THE OTHER END WALL OF SAID CASING; SUBSTANTIALLYU-SHAPED MIXING ELEMENTS MOUNTED ON THE END FACES OF SAID ROTOR AND ONTHE INTERIOR SURFACES OF SAID END WALLS, SAID MIXING ELEMENTS BEINGARRANGED IN CONCENTRIC ROWS WITH THE MIXING ELEMENTS ING ANY GIVEN ROWBEING CIRCUMFERETIALLY SPACED FROM EACH OTHER, EACH OF SAID MIXINGELEMENTS COMPRISING A PAIR OF RADIALLY ALIGNED AND RADIALLY SPACED LEGSCONNECTED BY A WEB, THE WEBS OF SAID MIXING ELEMENTS BEING MOUNTED ONSAID END FACES AND SAID INTERIOR SURFACES, RESPECTIVELY, AND PROJECTINGTHEREABOVE, THE RADIAL SPACING BETWEEN THE LEGS OF EACH MIXING ELEMENTBEING SUBSTANTIALLY GREATER THAN THE RADIAL THICKNESS OF THE LEGSWHEREBY WHEN THE LEGS OF ANY ONE MIXING ELEMENT ARE INTERFITTED WITH THELEGS OF ANOTHER MIXING ELEMENT SPACES OF SUBSTANTIAL WIDTH ARE FORMEDBETWEEN ADJACENT LEGS; FASTENING MEANS SECURING THE WEB OF EACH OF SAIDMIXING ELEMENTS TO ITS ASSOCIATED END FACE OR INTERIOR SURFACE, SAIDFASTENING MEANS HAVING AN ENLARGED HEAD OVERLYING AND PROJECTING AWAYFROM THE WEB OF ITS ASSOCIATED MIXING ELEMENT, SAID HEAD HAVING ADIAMETER SUBSTANTIALLY LARGER THAN THE RADIAL WIDTH OF THE LEGS, SAIDHEAD BEING SPACED A PREDETERMINED AXIAL DISTANCE FROM THE FREE ENDS OFTHE LEGS OF THE MIXING ELEMENTS OPPOSED THERETO; THE ROWS OF MIXINGELEMENTS ON SAID ROTOR BEING OFFSET RADIALLY FROM THE ROWS OF MIXINGELEMENTS ON SAID INTERNAL SURFACES SO THAT THE LEGS OF MIXING ELEMENTSIN ANY GIVEN ROW ARE INTERFITTED WITH AND OVERLAP THE LEGS ON THE MIXINGELEMENTS OPPOSED THERETO, WHEREBY, WHEN SAID ROTOR IS ROTATED, EACH TIMEA LEG OF ONE MIXING ELEMENT MOVES BETWEEN THE LEGS OF THE MIXING ELEMENTOPPOSTED THERETO THE MATERIAL BEING FORWARDED THROUGH THE CASING WILL BEMOVED INTO THE SPACES BETWEEN THE LEGS AND AGAINST AN EDGE OF THE WEBAND THENCE BETWEEN THE HEAD AND THE FREE END OF THE MIXING ELEMENT LEGSO THAT THE MATERIAL WILL BE SUBJECTED TO AN INTENSIVE SHEARING AND AVARIABLE COMPRESSION IN ORDER TO EFFECT A UNIFORM MIXING THEREOF.